// Using single quotes will print the variable name, not the value
echo ‘foo is $foo’; // 当使用单引号时,变量也将原样照印,显示结果 foo is $foo

// If you are not using any other characters, you can just echo variables
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz

//最有用的echo用法,使用<<<加上标识符来开始一段输出,引号不用转义表示,可直接输出.记得结尾要用同样的标识符结束

echo <<<END
This uses the “here document” syntax to output
multiple lines with $variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!
END;

// Because echo does not behave like a function, the following code is invalid.
($some_var) ? echo ‘true’ : echo ‘false’;

// However, the following examples will work:
($some_var) ? print ‘true’ : print ‘false’; // print is also a construct, but
// it behaves like a function, so
// it may be used in this context.
echo $some_var ? ‘true’: ‘false’; // changing the statement around
?>